Doug Engelbart, one of Silicon Valley’s best-known innovators, has died, according to his family. He was 88.

Engelbart is widely credited as the father of the computer mouse, which he developed along with other inventions while a researcher at Stanford Research Institute in Menlo Park, California.

He gave a celebrated public showing of his research at what was called the ”mother of all demos” in San Francisco in 1968, an event that foreshadowed computer usage models that would become common many years later in products like Apple’s Macintosh.

Word of Engelbart’s death prompted a large outpouring of messages on Twitter messages.

Mitch Kapor, an investor and software pioneer, tweeted that Engelbart was “a personal hero, to whom we owe virtually everything in computing.”

Futurist Paul Saffo said Engelbart “was ahead of his time to the very end.”